Telephone traffic recording system



Jan. 22, 1946. J. E. OSTLINE TELEPHONE TRAFFIC RECORDING SYSTEM FiledJan. 22, 1944 16 Sheets-Sheet l mum mwzzvrozz JOHN E. OSTLINE I .BY

ATTORNEY Jan. 22, 1946. J. E. OSTLINE 3 3 TELEPHONE TRAFFIC RECORDINGSYSTEM Filed Jan. 2 2, 1944 16 SheetsSheet 2 AIS m INVENTOR. y JOHN E.OSTLINE ATTORNEY I Jan. 22, 1946. J. E. OSTLINE 2,393,403

TELEPHONE TRAFFI C REbORDING SYSTEM Filed Jan. 22, 1944 1a She ets-Sheet5 FIG. 2A

I u m INVENTOR. 2 8:8; JOHN E. OSTLINE ATTORNEY Jan. 22, 1946. J. E.OSTLINE TELEPHONE TRAFFIC RECORDING SYSTEM Filed Jan. '22, 1944 1aSheets-Sheet 4 Ea vfi kmflo MNO Ev p L. 8m. mnn vma m5 mam m N G h 3 mum, mmvmx JOHN E OSTLINE ATTORNEY- Jan. 22, 1946. J. E. O'STLINE TELEPHONETRAFFIC RECORDING SYSTEM Filed Jan. 22, 1944 16 Sheets-Sheet 5 SEE E 595m QE INVENTOR. JOHN E. OSTLINE ATTORNEY 2, 1946'. J. E. OSTLINETELEPHONE TRAFFIC RECORDING SYSTEM Filed Jam. 22, 1944 16 Sheets-Sheet 6INVEN TOR. JOHN E. OSTLINE ATTORNEY Jan. 22, 1946. .1. 5., OSTLINETELEPHONE TRAFFIC RECORDING SYSTEM Filed Jan. 22, 1944 16 Sheets-Sheet 7CABLE TO PRINTER FIG. 9

IN VEN TOR. JOHN E. OSTLINE ATTORNEY Jan- 4 Y J. E. OSTLINE TELEPHONETRAFFIC RECORDING SYSTEM Filed Jan. 22, 1944" 16 Sheets-Sheet 8 CABhE TOPRINTER FIG.9

INVENTOR! JOHN E. OSTLINE TTORNEY Filed Jan 22, 1944 16 Sheets-Sheet 9 a6E mmhzEa Oh M 5.

INVENTOR. JOHN E. OSTLINE ATTORNEY 16 Sheet-Sheec 10 JOHN E. OSTLINE J.E. OSTLINE Filed Jan. 22, 1944 'IELEPHONE TRAFFIC RECORDING SYSTEM Jan.22, 1946.

0 3w mm? w wmm TE A o M j 0 0 0 0 8 80 mm 3 m6 m oE. m3 u n T|J.| m E xm v H FHN O NV. L aw 1 66 M 2w L 03 5:8 1 mwwi .6 n M6 66 u I n f6 5 03u 8 919: .32 u a ww m2: .8 0mm m m 2.? -w wwsm 6T :8 unm Emmnm mat mEzEmq. 8w 2b in 5 MU oh H 3 ATTORNEY Jan. 22, 1946.

E. OSTLINE 2,393,403

TELEPHONE TRAFFIC RECORDING SYSTEM 16 Sheets-Sheet 11 Filed Jan. 22,1944 TERMINAL IKOOK CABLE TO I PRINTER nae INVENTOR. JOHN E. OSTLJNEATTORNEY Jan. 22, 1946,

J. E. OSTLINE TELEPHONE TRAFFIC RECORDING SYSTEM Filed Jan. 22, 1944 16Sheets-Sheet 12 JOHN E. OSTLINE ATTORNEY Jan. 22, 1946. J. a. OSTLINE 2,TELEPHONE TRAFFIC RECORDING SYSTEM Filed Jan; 22, 1944 16 Sheets-Sheetl3.

INVENTOR. JOHN E. OSTLINE ATTORNEY .Jan. 22, 1946. I osT 2,393,403

I TELEPHONE TRAFFIC RECORDING SYSTEM RECORDING CHART FIG. I2 AO|2345167895520123456789i30l23456789H30l23456789i550|23456789i; 7 J3 4200 000000 80 0 0 00000 0.00000000' 0 0000 0 00 O0 9 00 0000000 0 0000000 00'0000000O 0000 0 000 0 9 l5 0 0 0 00 0 000 000 000 0040 0 I005.... .05. lo 90 I5 0 0 0 0 0 000 000 0 0 00 0 00 00 .0 0005 lo 00 3o0 0 0 0 000 000 0 0 0 0 0 lo 00000 00000 '00000 00 00 0 0H .00 00 0 000|0 IO 00 30 FIG. I20 1 Ol23456789 Ol234567 89 Ol2342501234567890|23456789 M23425? 7 I3 42 0000000000 000 0 0 I500 00000 0 0 0 0 0 0 0'9 46 0o 0000000000 000 0 0 v '500 00000 0 0 0 0 0 0 0' 9 46 0000 00000000 0 0 0 0 '0 .l 7 I0 00 I5 0000 0000 0000 0 0 0 0 00000 00 00000000 00' 00.30 0000 0000 0000 0 0 0 0 300000 00 00000000 0 I0 00 45 OI23456789Ol23456789 0123456789 O l23456789 023456789551 L; I3 42 0.000000 0000000 00000 '0 000 000000 00000 0 lo 00 I5 0 00000000 000000 Y 00000 0000000000 0 00 .4 6 IO 00 3O 0 00000000 000000 00000 0 000 000000 000000 IO 00 45 INVENTOR.

JOHN E. OSTLINE i Y BY ATTORNEY I J. E. os'rLnyE TELEPHONE TRAFFICRECORDI NG SYSTEM Jan. 22, 1946.

Filed Jan. 22, 1944 16 Sheets-Sheet 1e 7 FIG :3 J

, RUNK TERMINAL PINS TRAFF ER INVENTOR. 7 JOHN E. osrum: Z Z

Patented Jan. 22, 1946 TELEPHONE Tame RECORDING SYSTEM John E. stline,Chicago, Ill., assignor to Automatic Electric Laboratories, Inc.,Chicago, III., a corporation of Delaware Application January 22, 1944,Serial No. 519,251

42 Claims. The present invention relates ingeneral to traflic recordingequipment for telephone, or like,

systems and, more particularly, to improvements in apparatus forautomatically testing and recording at regular intervals the busytrunksin one or more trunk groups associated with theapparatus.

One 01 :the principal operating and maintenance requirementsinautomatic-telephone systems is that of knowing the volume of traflic forwhich the trunks and switches are to be provided. As a telephoneexchange or network increases in size, or as various classes of trafilcchange from one period to another, it becomes necessary to addto,subtract from, or re-arrange existing switching and trunk equipment tomeet these changing traffic conditions. Therefore, periodic trailicstudies become a necessary routine for trailic engineering purposes.

Methods of obtaining information relative to the duration and amount of.calls in each trunk and switch group in the busy hour have varied fromtime to time. The most obvious method is, of course, that of observingthe traffic manually by means of a stop watch. It is seldom used, due tothe relative slowness with which representative amounts of observationscan be accumulated.

Another method of obtaining holding time measurements is by recorderswhich mechanically and electrically indicate the holding time of eachcall in a group of switches or trunks during a certain time interval.These recorders, of which there are several types, usually have onecommon feature consisting of a paper tape moving at a pre-determinedspeed on which the length and the amount of :calls are indicated bymeans of recording pens. The chief disadvantage with all devices of thistypevresides in the fact that the records obtained are of no use untilconsiderable time and laboris expended in measuring, interpreting andsummarizing the recorded results into fundamental quantities, and

even then these results will beinfiuenced-by some guess work and errorsdue to manual interpretations.

In order to overcome the, disadvantage and limitations of the foregoingmethods, and to make possible arapid accumulationqof fundamental trafiicdata on a considerable amount of calls, a method referred tofas .switchcounts" has for a number of years been used. This method consists ofplacing one or more-trunk groups an observer who counts and records atfixed regular intervals the amount of switches held in an operated orbusy condition. Such data, when obtained in suflicient quantities, willindicate the average load in any switch or trunk group and by arelatively simple formula the unit calls carried by the trunk group canthus be obtained. This figure once having been ascertained, aconsultation of standard tramc tables will indicate whether a groupneedsadjusting or it it is satisfactory for handling the ofieredtraflic.

As in the case of mechanicallytape recorded data, this second method ofobtaining traflic data, by manual observation has a number ofdisadvantages. The principal one of these is that the human element isalways a variable factor and in addition the effectiveness of thismethod depends upon the frequency and regularity of each scanningoperation, that is, the counting of busy switches during each period. Inorder to obtain this information correctly and in order to cover as manytrunk groups as possible at the same time, many observers may berequired. It. is also found desirable to not only record the amount oftrunks busy in the group, but also to identify the particular trunkswhich are busy. This information is desirable in order to determine ifthe observed graded" groups are properly distributed or if they needre-aclJusting.

It is an object of the present invention to provide an improved unit ofapparatus, whereby switch counts are made, added and recordedautomatically. This unit of apparatus hereinafter referred to asTrafilcorder, scans each trunk group under observation at regular fixedintervals. The data obtained from each scanning is then stored, analyzedand recorded in printed form comprising numeral characters.

This data can, without any further analyzation or prolonged study, beused to ascertain if a trunk group or groups under observation requiresany re-adjustment or not.

Another object of the invention is to provide an improved automatictesting-and recording apparatus, which is operated to record in printednumerals a printed record designating, or identifying, each trunk andits idle or busy condition at periodic pre-determined timed intervals,the number of trunks in each trunk group and the number of such trunkswhich arebusy at given pre-determi'ned timedlintervals, the date andtime and the total number 01 busy trunks in each to be studied undermanual visual observation by 56 trunk group for a period oftimecomprising a pre-determined numberof' the periodic timed .number of:trunks arranged in one or more groups.

Another object of the invention is to provide circuits and apparatus toprint a typewritten record comprising a heading," a plurality ofperiodic trunk recordings, and a total recording. The heading comprisesnumerals and spacings designating the number of trunk groups, the numberof trunks in each group, the identity of each trunk ineach group and theday, month and year, The periodic trunk recordings comprising successivelines printed at pre-determined timed intervals, each line identifyingeach busy trunk and designating the number of busy trunks in each trunkgroup and the time of day.

The total recording is printed after the periodictrunk recordings andshows the total sum ofthe busy trunks in each of the trunk groups duringthe periodic trunk recording operations.

Further novel features believed to be characteristic of the inventionare set forth in the following description andin the appended claims.The invention, both as to its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the specification taken in connection withthe accompanying drawings in which Figs. 1A and 1B illustrate the wiringar-' rangements of the three scanning switches Al,

A2 and A3, and their associated controlling relays H10, H0, I20, thegang group relays GRI and GRZ and a portion of the storage relays SR.Figs. 2A and 2B, and 3A and 3B illustrate similar scanning switche Bl,B2 and B3 and Cl, C2 and C3 and their associated control relays; Fig. 33also diagrammatically represents three adders which are similar to theN0. adder shown in Fig. 4B; Fig. 4A illustrates the No. 1 adder and Fig.4B the No. 5 adder; Fig. 5 illustrates the timing apparatus comprisingan hours switch EU, a tens minute switch MT, a units minute switch MU,and a seconds switch SE and their associated relays and a time panel fordisplaying the time of day; ,Fig. 6 illustrates the primary switch PStogether with its control relays and start key K2.

Fig., .'7 illustrates the wiper controlled by the manually controlledkeys shown in. Fig. 11, the

time pulse unit'l50 and the cross connecting terminal block 195; Figs.8A and 8B illustrate the two counter switches LA and LB and theirassociated control relays; Fig. 9 illustrates thewiring arrangement ofthe recordprinterand Fig. 10 diagrammatically illustrates the mechanismof the record printer; Fig. 11 shows the time lamp panel, the manuallycontrolled keys comprising the date keys K3, K4, K5 and K6, the groupingkeys K1, K8, K9, KIO, Kl l, Kl2, KM, KN, Kl5 and KIB, the groupselecting key Kl, the start key K2 and the minutes and hours keys MK andHK; Figs. 12A, 12B, 12C and 12D show in part the kind of recordingcharts printed by the apparatus; and Fig. 13 shows a perspective view ofthis unit of apparatus, referred to as a Tramcorder.

Referring now more particularly to the drawings, the scanning switchesare of the well-known rotary switch type which operate their wipers onestep in response to the release of their associated stepping magnets.Each scanning switch has six wipers, the first one for controlling thestepping circuits, the second for controlling the circuits and apparatusto print the headings, such as shown in Figs. 12A, 12B, 12C and 12D, the3rd and 4th for controlling the circuits and apparatus to print thesecond and successive lines on the recording charts, the 6th forcontrolling the circuits to operate the adders to total the numher ofbusy trunk conditions encountered, and the 5th for controlling thecircuits and apparatus to print the total busy trunk conditions added bythe adders and shown in the last line on each recording chart. Trunkterminal pins 0 to 49, inclusive, shown at the extreme right of Fig. 1B,are cross connected by means of jumpers to the test conductors of thetrunks to be tested. The ganggroup relays GR! and GR2, when energized,connect these trunk test conductors to test conductors T0 to T49,inclusive. The storage relays SRO to SR49 are individually connected tocorresponding ones of these test conductors and are operated if thecorresponding trunk test conductors are grounded due to thecorresponding trunks being busy. The test conductors T0 to T49,inclusive, terminate in the bank contacts accessible to the fourth wiper01' each scanning switch and these wipers are connected by way ofconductor 654 to the primary switch PS (Fig. 6) for controlling Markrelay 510.

The second wiper of each scanning switch has access, by way of its bankcontacts, to printer conductors P9 to P9, inclusive, extending by way ofa cable to the printer magnets shown in Fig. 9. The second wipers of thescanning switches also have access to conductors extending by way of acable to Fig. 7 to the wipers of the grouping keys and these scanningwipers are connected by way of conductor 652' to the primary switch PSin Fig. 6.

The third wiper of each scanning switch has access to conductor BI'Iextending to the primary switch relay group (Fig. 6) and to conductorsextending to the counter switches for controllin the operation. of theprinter. Some of these wipers have access to conductors extending to thetime switches shown in Fig. 5. These wipers are connected by way ofconductor 653 to the primary switch PS. y

The sixth wiper of each scanning switch is connected by way of conductor656 to primary switch PS and has access to conductors extending to theadders for stepping the adder switches one step for each, busy trunkencountered. The fifth wipers of the scanning switches are connected byway of conductor 655 to the primary switch PS and have access toconductors extending to the adders for reading the total added b theadders.

The adders shown in Figs. 4A and 4B, and diagrammatically shown bysquares in Fig. 313, each comprise two rotary stepping switches of thewell-known type and a group of control relays. The switches HA and HCare stepped one step for each busy trunk encountered by the scanningswitches, while the switches HB and HD are stepped one step for eachbusy registrations. These switches have access to printer conductorsextending in a cable to the printer magnets shown in Fig. 9.

The time switches HU, MT, MU and SE in Fig. 5 are of the well-knownrotary type switches which step their wipers on the deenergization oftheir respective stepping magnets. One wiper of each of these timingswitches is connected by way of a cable to the scanning switches shownin asaa os conductors extending by way of a cable to the printer magnetsshown in F18. 9. Another set of wipers of these time switches areconnected to the lamps in the time lamp panel for displaying the time ofday. Relays Bill, 520 and 530 are proyided for switching over to theproper tens hour printer conductor. Time switch HU is pro- 1 vided withoil-normal springs 53 which are in normal open position when the wipersof the units hour switch .HU are in their first position. Theseoff-normal springs close when the wipers tactwith the rotating rollerI029. Cam I028 instantly turns through one-half revolution, and in sodoing, actuates the type bar I03! to print the numeral '9. Each cam,such as "128, is pivof this switch take their first step. The hours 1key HK and the minutes key MK corresponding 1 to the hours key, HK andthe minutes key MK shown in Fig. 11 are provided for manually settingthe time switches to correspond to the time of day.

Fig. 6 shows the primary switch PS and associated control relays. Theprimary switch P8 is of the well-known rotary type which steps itswipers on the deenergization of its stepping magnet. The start key .K2,corresponding to ke K2 in Fig. 11, is provided for initiating theoperation of the Trafllcorder after the time switches, the month and daykeys, and the grouping keys have been properly set,

Fig. 7 shows a plurality of key wipers controlled by the manually setcorresponding keys in Fig, 11 and a time pulse unit 150 which isoperative when ground is connected thereto for transmitting time pulsesevery seconds. The key wipers are connected by conductors extendingbyway of a cable to the scanning switches and these wipers have access toprinter conductors extending by way of a cable to the printer magnets inFig. 9. The key wiper Kl has access to conductors extending to thescanning switches for controlling certain of the scanning control relaysin accordance with the desired roupings of the trunks. A terminal block195 isshown in.

Fig. 7 connected to printer conductors extending to the printer magnetsand is arranged for cross connection by means of jumpers to conductorsextending to the scanning switches for designating the last two digitsof the year.

Figs. 8A and 8B show the counter switches LA and LB which are also ofthe well-known rotary type. The bank contacts of the counter switchesare connected by way of printer conductors to the printer magnets ofFig. 9. Fig. 8A shows a group of counter switch control relays forcontrolling the operation of the counter switches LA and LB.

Fig. 9 shows the printing magnets and driving motor of the recordprinter and Fig. 10 shows the mechanism associated with one of theseprinting magnets. This record printer is an electrically driventypewriter and is commonly known as the Electromatic" printer. ThtElectromatic printer comprises a motor driven typewriter such asdisclosed in Product Engineering for November, 1930, and in The StoryofElectromatic," published by the Electromatic Typewriters, Inc.,Rochester, New York. During the time the electromatic printers are inuse, the small electric motors for controlling the same are in constantoperation and are constantly operating the soft rubber rollers, such asroller I029, shown in Fig. 10. In order to operatethe electromaticprinter in this case, magnets POM to PQM, inclusive, and mark magnet PMAare added to control the key bars. In Fig. 10 magnet P9M operates itsarmature I026 to in turn actuate the key bar H121. This results inbringing the cam I028 into con:

oted at one end ofa bell crank forming part of the linkage it operates.Normally, a stop holds eachcam a few thousandths of an inch out ofcontact with the roller surface, but when the magnet correspondingto agiven cam is operated. a spring forces the serrated surface of the camagainst the soft rubber-surface of the roller and the two rotatetogether without slippage. In so doing, the cam pivot and the link towhich it is attached are forced away from the roller. this motion, forwhich the motor supplies the power, that actuates the type bar. Sincethe mechanical construction of the electromatic printer is not part ofthisinvention, it is believed that this general description of itsoperation will sufiice. Any further details regarding the mechanicaloperation of this type of printer may be had by referring to theaforesaid publications. All the letter type bars of this printer havebeen removed and only the numeral type bars 0 to 9, inclusive, and oneother type bar referred to as the Mark type bar having a small zero forindicating 'busy trunks remain because only these type bars are used inthe present invention. The carriage of the printer moves one step whenany type bar is actuated and also steps or spaces when the space magnetPSPM is actuated. The printer is provided with a printer ribbon controlmagnet PRCM which, when actuated, positions, the red mally opened whenthe carriage of the printer is in its normal position and closes as soonas the carriage moves in its first step. The printer motor 938 isactuated as long as the conductor- 936 is grounded.

Fig. 13 shows a perspective view of the portable 'Iraflicorder" having abox like enclosure for enclosing the equipment comprising the rotaryswitches and their associated relays. The combined lamp and key paneland the electromatic printer is shown mounted on the top of this unit.

Along the righthand side of the enclosure are provided trunk terminalpins to which the test trunks of the trunks to be tested are crossconnected by means ofjumpers. A pair of battery terminals and a pair offuses are also shown.

The "Traflicorder is a unit of apparatus which will collect, analyze andrecord in printed form all data required to ascertain the volume oftrafilc carried by each group of trunks under observation. This data isobtained by scanning each connected trunk group for busy trunks every 15seconds during the busy hour or any other periods for as long a time asmay be desired. The Trafficorder is arranged to observe traffic on amaximum of fifty trunks which may be grouped as follows: grouping No. 1for 5 groups 'of 10 trunks, grouping No. 2 for 3 groups of 16 trunks,grouping No. 3 fora groups of 25 trunks, grouping No. 4 for a singlegroup of 50 trunks.- The foregoing number of trunks in each trunk groupare the maximum, and, if desired, the number of trunks in each trunkgroup may be less for any group.

After connecting the desired trunks to the trunk terminal pins of theTramcorder and after op- Itls.

erating the manual keys of the key panel are set in accordance with thedesired trunk grouping, the minutes and hours keys are operated untilthe lamp panel displays the correct time of day. The start key K2 isthen operated to cause certain of the scanning switches, in accordancewith the grouping selected, to operate in a series of scanning cycles,or operations. The selected scanning switches, comprising three innumber, are operated through a. complete scanning. cycle every 15seconds. The first scanning cycle of the scanning switches causes aheading, such as shown in Fig. 12A to be printed across the recordsheet. This heading" shows the identity number of each connected trunk,the actual number of trunks in each group, the number of groups, and themonth, day and year. After this heading" is printed a second scanningcycle is automatically started and the primary switch PS takes one stepto alter the functions performed by these scanning switches. The secondand subsequent cycle operations of the scanning switches cause theprinting of the second and subsequent lines, such as shown on chart I2A. Each trunk found busy is identified by a mark. The number of busytrunks in each'trunk group is counted and this total is printed. Theclock time of these cycle operations is also printed. During these cycleoperations the number of busy trunks in each trunk group are added inthe respective adders and after sixty such cycle operations the totalsadded by the adders are printed on the chart as shown in the last lineof Fig. 12A.

Detail operation The first operation to be performed by the observer isto connect the test conductors of the trunks to be observed to the trunkterminal pins shown to the right on Fig. 1B. To do this the observerwheels the Trafflcorder to some distributing frame, or distributingpoint, and then jumpers only the test conductors of the trunks to beobserved to the trunk terminal pins to 49, inclusive, as shown in Fig.1B. The observer also connects the negative and positive battery busbars of the exchange battery to the battery terminals on the Tramcorder.

The next operation is to operate the group selecting key KI to select aparticular grouping. The Traflicorder is arranged to observe trafflc ona maximum of 50 trunks which can be grouped as follows:

Grouping #1-five groups of ten trunks each, Grouping #2three groups of16 trunks each, Grouping #3two groups of 25 trunks each, Grouping #4onegroup of 50 trunks.

The observer now sets the key Kl, shown in Fig. 11, to the numbercorresponding to the desired grouping. The wipers KI and KI (Fig. '7)are associated with the key KI and are operated to correspondingpositions.

Assuming that the ke Kl is operated to its #1 position then the wiper KIis operated into engagement with conductor III in Fig. 7 for theset totheir "0" positions. This operation or the keys divides the fifty trunksinto five groups of ten trunks each. Referring now to Fig. 7, the wipersKI K8, K9, KM and KM are each set to their second positions inengagement with the Pl conductor which extends to the #1 printer magnetPIM shown in Fig. 9. It should be mentioned that the wipers such aswiper K1 is moved at the same time that the key K1 is manually moved bythe observer. In the same manner the wipers, which are shown primed,operate at the same time as the correspondingly indicated key. 'The keysKI2, KI3, KM, KIS and KIG and theircorresponding primed wipers shown onFig. '1 are each operated to their last positions inengagement with theconductor P0 which extends to the #0 printer magnet POM shown in Fig. 9.

In response to grounding the'conduotor IN, the time pulse unit I50 isoperated-to ground conductor I00 every fifteen seconds or four times perminute. The grounding of conductor 10! also completes a circuit forstarting the printer motor 938 over a circuit as follows: from groundedconductor IM to the printer motor start conductor 930 included in theprinter cable which extends to Fig. 9 and thence by way of conductor 936to the printer motor 938 to battery. The grounding of conductor I0l alsocompletes a circuit for the printer carriage return magnet PCRM it thecarriage of the printer is oiI-normal as follows: from groundedconductor 10!, contact 68! of start relay 660, printer oilfnormalconductor 935 to the printer ofi-normal contacts 931 and to the windingof the printer carriage return magnet PCRM to battery. The operation ofthe printer carriage return magnet PCRM will return the printer carriageto its initial typing position as well as advancing the recording sheetone vertical spacing step. Grounded conductor IOI also grounds the HU3,the MT3, the MU3, and the SE4 wipers of the time displa switches shownin Fig. 5. Assuming that these wipers at this time are in the positionshown in Fig. 5, the grounding of these wipers will complete circuitsfor the #0 unit hours lamp, the #0 tens minute lamp, the #0 unit minuteslamp, and the #00 seconds lamp shown in the time display panel of Fig.5.

In the lower portion of Fig. 5 are shown the minute key MK and the hourkey HK which are provided for the purpose of directly operating thestepping magnets of the minutes and hours time switches so as tomanually set the time display to correspond with the actual time of daythe observation is to be taken.

As shown in Fig. 5 the tens minute switch MT and the units minute switchMU are both in 0 position thereby lighting the 0 tens and 0 unitsminutes lamps. Assuming that the time is 9:45 a. m., the minute key MKis operated forty-five times to operate the stepping magnet 560 of theunit minute switch MU over the following circuit: from groundedconductor 10! thru the spring contacts of the minute key MK and fromthence to the winding of stepping magnet 560 to battery. On eachdeenergization of the stepping magnet 560 the unit minute switch MUoperates its wipers MUI, MU2, and MU3 one step. When wiper MUI reachesits tenth position a circuit is prepared for operating the steppingmagnet 550 of the tens minute switch at contacts 562. The next timestepping magnet 560 is energized, the contacts 562 completea circuitfrom the grounded wiper MUI by way of the tenth bank contact to thewinding

